1. Field of the Invention
This invention relates generally to wells for the production of petroleum products and more particularly concerns lateral branches from a primary wellbore. More specifically the present invention concerns the provision of a method and apparatus for landing and orienting downhole tools at well depths established by casing nipples to enable the efficient conduct of subsequent downhole operations. As a more specific example, the present invention is useful during the operation of providing multilateral branches from a primary wellbore and their future reentry through the casing string of the well. Even more specifically the invention concerns the provision of a method and apparatus having the principal function of positioning, orienting and locking milling or deflection assemblies relative to a selected landing and orienting joint of the casing string of the well and locking the apparatus within the landing profile of the selected landing and orienting joint.
2. Description of the Related Art
In oil and gas production wells, or water or steam wells, conventional side-tracking methods that have been used to drill lateral branches from a parent wellbore generally require the setting of a temporary locating device within the casing of the parent wellbore. A temporary locating device for this purpose may be a plug, whipstock or any suitable type of expanding means that is anchored within the well casing by frictional engagement with the inner surface of the casing. These plugs are sometimes unstable due to their frictional retention within the casing, so they cannot be relied on to provide a reliable depth and orientation reference within the casing. Also, when frictional plugs or whipstocks of this nature are removed from the casing, their depth and angular reference for lateral branching is lost. Thus, to reenter a lateral branch that has been drilled, the depth and angular reference must be accurately reestablished. This is often a difficult, time consuming and expensive procedure that adversely influences the cost of well completion. Therefore, it is desirable to provide the well casing with means for establishing a permanent depth and angular reference and known orientation from which lateral branches can be selectively reentered. It is also desirable to simplify the construction of multiple lateral wellbore branches and to reduce the risk of failure during the side-tracking process.
Until a number of years ago virtually all wells drilled and completed for production of petroleum products were vertical wells. More recently it has been found to be quite beneficial to drill and complete horizontal or lateral wellbores so that a substantial length of the wellbore will be present in a productive formation and thus, particularly in marginal zones, will provide greater opportunity to produce the petroleum products that are present therein. Horizontal drilling procedures and equipment have been developed to drill wellbores which are diverted from the vertical at a particular depth and result in the location of a section of wellbore which is at or near the horizontal or which is selectively oriented for positioning in a production zone. Well drilling and completion procedures and equipment have more recently been developed to accomplish drilling of multilateral branches from wells, typically wells having wellbores that are lined with well casing. Typically multilateral branches are drilled by first milling a window in the casing at a desired depth. A milling whipstock is located within the well casing at a selected depth and provides an orienting geometry for orienting and deviating a casing milling tool in a manner designed to achieve the milling of a casing window having a desired angle for subsequent lateral branch drilling operations at a desired lateral branch angle and a desired azimuth. Lateral branches of the well are then drilled from one or more casing windows and are completed in a manner accomplishing desired production of petroleum products.
After casing windows have been milled and a drilling whipstock facilitating milling of a casing window and drilling of a lateral branch wellbore has been removed from the well casing, when reentry of a casing window is desired, it has been found exceedingly difficult to locate such windows and to locate equipment within the well casing at the proper depth and in the proper position for entering the casing windows and accomplishing lateral branch operations. For lateral branch reentry a deflection tool, i.e., drilling whipstock, deflector whipstock or the like must be precisely positioned at a desired well depth and must be precisely rotationally oriented with respect to the desired azimuth of the lateral branch to be drilled. Such positioning is quite difficult and time consuming to accomplish. Even in the case of small errors in deflector location, it is likely that the reentry tool will miss the casing window or become lodged on the edges of the window. It is also likely that these small errors will cause the tool to be misdirected slightly from the standpoint of azimuth or inclination so that the branch wellbore is not precisely tracked by the tool. It is desirable therefore to provide means for positively locating branch wellbore drilling and completion equipment within a well casing to facilitate drilling of lateral branch wellbores and which, subsequent to removal of branch wellbore drilling equipment from the well casing, facilitates precise depth location and precise rotational orientation of various types of equipment for precision lateral branch reentry. It is further desirable to provide means for efficient drilling and completion of lateral branch wellbores to facilitate simple and efficient preparation of a well having multilateral branch wellbores at selected depths and azimuths for completion and subsequent production, as well as providing for efficient reentry of selected multilateral branches for well servicing activities.